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.TH PTHREAD_GETSCHEDPARAM 3C "February 21, 2023"
.SH NAME
pthread_getschedparam, pthread_setschedparam \- access dynamic thread
scheduling parameters
.SH SYNOPSIS
.nf
cc -mt [ \fIflag\fR... ] \fIfile\fR... -lpthread [ \fIlibrary\fR... ]
#include <pthread.h>

\fBint\fR \fBpthread_getschedparam\fR(\fBpthread_t\fR \fIthread\fR, \fBint *restrict\fR \fIpolicy\fR,
     \fBstruct sched_param *restrict\fR \fIparam\fR);
.fi

.LP
.nf
\fBint\fR \fBpthread_setschedparam\fR(\fBpthread_t\fR \fIthread\fR, \fBint\fR \fIpolicy\fR,
     \fBconst struct sched_param *\fR\fIparam\fR);
.fi

.SH DESCRIPTION
The \fBpthread_getschedparam()\fR and \fBpthread_setschedparam()\fR functions
allow the scheduling policy and scheduling parameters of individual threads
within a multithreaded process to be retrieved and set. Supported policies are
:
.sp
.ne 2
.na
\fB\fBSCHED_OTHER\fR\fR
.ad
.RS 15n
traditional time-sharing scheduling class
.RE

.sp
.ne 2
.na
\fB\fBSCHED_FIFO\fR\fR
.ad
.RS 15n
real-time class: run to completion
.RE

.sp
.ne 2
.na
\fB\fBSCHED_RR\fR\fR
.ad
.RS 15n
real-time class: round-robin
.RE

.sp
.ne 2
.na
\fB\fBSCHED_IA\fR\fR
.ad
.RS 15n
interactive time-sharing class
.RE

.sp
.ne 2
.na
\fB\fBSCHED_FSS\fR\fR
.ad
.RS 15n
fair-share scheduling class
.RE

.sp
.ne 2
.na
\fB\fBSCHED_FX\fR\fR
.ad
.RS 15n
fixed priority scheduling class
.RE

.sp
.LP
See \fBpthreads\fR(7). The affected scheduling parameter is the
\fIsched_priority\fR member of the \fBsched_param\fR structure.
.sp
.LP
The \fBpthread_getschedparam()\fR function retrieves the scheduling policy and
scheduling parameters for the thread whose thread \fBID\fR is given by
\fIthread\fR and stores those values in \fIpolicy\fR and \fIparam\fR,
respectively. The priority value returned from \fBpthread_getschedparam()\fR is
the value specified by the most recent \fBpthread_setschedparam()\fR or
\fBpthread_create()\fR call affecting the target thread, and does not reflect
any temporary adjustments to its priority as a result of any priority
inheritance or ceiling functions. The \fBpthread_setschedparam()\fR function
sets the scheduling policy and associated scheduling parameters for the thread
whose thread  \fBID\fR is given by \fIthread\fR to the policy and associated
parameters provided in \fIpolicy\fR and \fIparam\fR, respectively.
.sp
.LP
If the \fBpthread_setschedparam()\fR function fails, no scheduling parameters
will be changed  for the target thread.
.SH RETURN VALUES
If successful, the \fBpthread_getschedparam()\fR and
\fBpthread_setschedparam()\fR functions return  \fB0\fR. Otherwise, an error
number is returned to indicate the error.
.SH ERRORS
The \fBpthread_getschedparam()\fR and \fBpthread_setschedparam()\fR functions
will fail if:
.sp
.ne 2
.na
\fB\fBESRCH\fR\fR
.ad
.RS 9n
The value specified by \fIthread\fR does not refer to an existing thread.
.RE

.sp
.LP
The \fBpthread_setschedparam()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value specified by \fIpolicy\fR or one of the scheduling parameters
associated with the scheduling policy \fIpolicy\fR is invalid.
.RE

.sp
.ne 2
.na
\fB\fBEPERM\fR\fR
.ad
.RS 10n
The caller does not have the appropriate permission to set either the
scheduling parameters or the scheduling policy of the specified thread.
.RE

.SH ATTRIBUTES
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Committed
_
MT-Level	MT-Safe
_
Standard	See \fBstandards\fR(7).
.TE

.SH SEE ALSO
.BR pthread_attr_init (3C),
.BR sched_get_priority_max (3C),
.BR sched_get_priority_min (3C),
.BR sched_getparam (3C),
.BR sched_getscheduler (3C),
.BR sched_setparam (3C),
.BR sched_setscheduler (3C),
.BR attributes (7),
.BR pthreads (7),
.BR standards (7)
